This invention relates generally to apparatus for machining and fusing plastic pipe and more particularly concerns the fusion of the ends of concentric pipes to a base member.
Apparatus for joining plastic pipe in end to end relationship is disclosed in U.S. Pat. No. 4,352,708. That apparatus includes a clamp holding a first section of pipe in fixed position and a second movable clamp holding the second section of pipe to bring it into position for fusion to the first section of pipe. The introduction of a third section of pipe concentric with the first introduces complications not addressed by that apparatus. In the present application, the end faces of a plastic cylinder and a plastic piston are to be fused to a plastic base member without fusing the exterior cylindrical surface of the piston to the interior cylindrical surface of the cylinder. Using the teachings of the previous patent, the base member and the cylinder may be gripped in the moving and fixed clamps respectively and machined, heated and fused under controlled pressure. However, with no means for gripping the cylindrical surface of the piston, the piston is free to rotate under the force exerted by a rotating facing cutter used to simultaneously trim the cylinder and piston end faces. The piston is also subject to an axial force exerted upon it during the application of controlled pressure in the fusion process and to an opposite or pulling axial force exerted upon it by the axial withdrawal of the heater from the softened faces to be fused. There is no prior art device which provides for the gripping of the interior pipe or piston so as to overcome the effect of these forces.
It is, therefore, an object of the invention to provide apparatus useful in the machining and fusion of concentric plastic pipes to a base member. Another object of the invention is to permit fusion of the end walls of a plastic cylinder-piston combination to a plastic base member without causing the cylindrical surfaces of the cylinder and piston to be fused together.